Field of the Invention
This invention relates to a composition and method to improve hydrocarbon recovery during a hydrocarbon production operation. More specifically, this invention relates to a composition and method to increase the flash point of wettability alteration chemicals introduced into injection wells.
Description of Background Art
Whenever the bottom-hole flowing pressure of a well drilled in gas-condensate reservoir drops below the dew point, liquid hydrocarbons in the form of condensate accumulates near the wellbore area and forms a condensate bank. As the liquid hydrocarbon saturation in the near-wellbore region increases, the gas relative permeability is decreased. This results in loss of productivity of both gas and condensate. Over time, nearly all gas wells will accumulate condensate or water blockage near the wellbore. In rich gas-condensate reservoirs that have a permeability of less than 100 mD, the formation of condensate banks is even more problematic. Water can also accumulate near the wellbore area due to water flowing from the hydrocarbon reservoir and water aquifers, filtrate water from drilling mud, and water being injected into the wellbore during other operations associated with hydrocarbon production, creating a water bank. Condensate banks and water banks can occur separately or simultaneous and are collectively referred to herein as condensate and water banks.
Several techniques have been used to attempt to remediate the problem of condensate and water banks. These methods include gas cycling, drilling horizontal wells, hydraulic fracturing, acidizing, injection of super critical CO2, and the use of solvents and wettability alteration chemicals. Gas cycling keeps the reservoir pressure higher than the dew point to reduce the liquid drop out. This method is limited by the volumes of gas that can be re-cycled in the reservoir. In order for an ideal recycle, the gas volume injected into the reservoir will be larger than the total gas that can be produced from such a reservoir.
Other approaches for remediating the problem of condensate and water banks are drilling horizontal wells, acidizing and hydraulic fracturing where the pressure drop around the wellbore area is lowered to allow for a longer time of production before the reservoir pressure drops below the dew point. These approaches are costly as they require drilling rigs and they are still a temporary solution for this problem.
Another technique for remediating the problem of condensate and water banks is the use of solvents. Solvents have the potential to remove condensate and water banks around a wellbore. This would allow gas flow to be unimpeded through the near-wellbore region, resulting in smaller drawdown and slower accumulation of condensate. However, the durability of solvents is questionable and the low flash point of some solvent compounds represents a hazardous source of fire and explosion. Moreover, wettability alteration needs to be approached very carefully not to cause permanent damages to the reservoir.